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design steps of overhead rectangular water tank pdf
#1

INTRODUCTION
Storage reservoirs and overhead tank are used to store water, liquid
petroleum, petroleum products and similar liquids. The force analysis of
the reservoirs or tanks is about the same irrespective of the chemical
nature of the product. All tanks are designed as crack free structures to
eliminate any leakage. Water or raw petroleum retaining slab and walls
can be of reinforced concrete with adequate cover to the reinforcement. Water and petroleum and react with concrete and, therefore, no special
treatment to the surface is required. Industrial wastes can also be
collected and processed in concrete tanks with few exceptions. The
petroleum product such as petrol, diesel oil, etc. are likely to leak through
the concrete walls, therefore such tanks need special membranes to
prevent leakage. Reservoir is a common term applied to liquid storage
structure and it can be below or above the ground level. Reservoirs below
the ground level are normally built to store large quantities of water
whereas those of overhead type are built for direct distribution by gravity
flow and are usually of smaller capacity.
1.1 OBJECTIVE
1. To make a study about the analysis and design of water tanks. 2. To make a study about the guidelines for the design of liquid retaining
structure according to IS Code. 3. To know about the design philosophy for the safe and economical
design of water tank. 4. To develop programs for the design of water tank of flexible base and
rigid base and the underground tank to avoid the tedious calculations. 5. In the end, the programs are validated with the results of manual
calculation given in Concrete Structure book.

A water tank is used to store water to tide over the daily requirement. In the
construction of concrete structure for the storage of water and other liquids
the imperviousness of concrete is most essential .The permeability of any
uniform and thoroughly compacted concrete of given mix proportions is
mainly dependent on water cement ratio .The increase in water cement ratio
results in increase in the permeability .The decrease in water cement ratio
will therefore be desirable to decrease the permeability, but very much
reduced water cement ratio may cause compaction difficulties and prove to
be harmful also. Design of liquid retaining structure has to be based on the
avoidance of cracking in the concrete having regard to its tensile strength.
Cracks can be prevented by avoiding the use of thick timber shuttering
which prevent the easy escape of heat of hydration from the concrete mass
.the risk of cracking can also be minimized by reducing the restraints on
free expansion or contraction of the structure.
1.1 OBJECTIVE
1. To make a study about the analysis and design of water tanks.
2. To make a study about the guidelines for the design of liquid retaining
structure according to IS Code.
3. To know about the design philosophy for the safe and economical
design of water tank.

4. To develop programs for the design of water tank of flexible base and
rigid base and the underground tank to avoid the tedious calculations.
5. In the end, the programs are validated with the results of manual
calculation given in .Concrete Structure.

2.1SOURCES OF WATER SUPPLY :
The various sources of water can be classified into two categories:
Surface sources, such as
1. Ponds and lakes;
2. Streams and rivers;
3. Storage reservoirs; and
4. Oceans, generally not used for water supplies, at present.
Sub-surface sources or underground sources, such as
1. Springs;
2. Infiltration wells ; and
3. Wells and Tube-wells.
3.1Water Quantity Estimation
The quantity of water required for municipal uses for which the water supply scheme has
to be designed requires following data:
Water consumption rate (Per Capita Demand in litres per day per head)
Population to be served.
Quantity= Per demand x Population
3.2 Water Consumption Rate
It is very difficult to precisely assess the quantity of water demanded by the public, since
there are many variable factors affecting water consumption. The various types of water
demands, which a city may have, may be broken into following class
Water Consumption for Various Purposes:
Types of Consumption Normal Range
(lit/capita/day)
Average %
1 Domestic Consumption 65-300 160 35
2 Industrial and Commercial
Demand
45-450 135 30
3 Public including Fire Demand
Uses
20-90 45 10
4 Losses and Waste 45-150 62 25

3.3 Fire Fighting Demand:
The per capita fire demand is very less on an average basis but the rate at which the water
is required is very large. The rate of fire demand is sometimes treated as a function of
population and is worked out from following empirical formulae:
Authority Formulae (P in thousand) Q for 1 lakh
Population)
1 American
Insurance
Association
Q (L/min)=4637 P (1-0.01 P)

41760
2 Kuchling's
Formula Q (L/min)=3182 P

31800
3 Freeman's
Formula Q (L/min)= 1136.5(P/5+10) 35050
4 Ministry of
Urban
Development
Manual Formula
Q (kilo liters/d)=100 P for P>50000
31623
3.4 Factors affecting per capita demand:
Size of the city: Per capita demand for big cities is generally large as compared to
that for smaller towns as big cities have sewered houses.
Presence of industries.
Climatic conditions.
Habits of economic status.
Quality of water: If water is aesthetically $ people and their
medically safe, the consumption will increase as people will not resort to private
wells, etc.
Pressure in the distribution system.
Efficiency of water works administration: Leaks in water mains and services;
and un authorised use of water can be kept to a minimum by surveys.
Cost of water.
Policy of metering and charging method: Water tax is charged in two different
ways: on the basis of meter reading and on the basis of certain fixed monthly rate.

3.5 Fluctuations in Rate of Demand:
Average Daily Per Capita Demand
= Quantity Required in 12 Months/ (365 x Population)
If this average demand is supplied at all the times, it will not be sufficient to meet the
fluctuations.
Seasonal variation: The demand peaks during summer. Firebreak outs are
generally more in summer, increasing demand. So, there is seasonal variation .
Daily variation depends on the activity. People draw out more water on Sundays
and Festival days, thus increasing demand on these days.
Hourly variations are very important as they have a wide range. During active
household working hours i.e. from six to ten in the morning and four to eight in
the evening, the bulk of the daily requirement is taken. During other hours the
requirement is negligible. Moreover, if a fire breaks out, a huge quantity of water
is required to be supplied during short duration, necessitating the need for a
maximum rate of hourly supply.
So, an adequate quantity of water must be available to meet the peak demand. To meet all
the fluctuations, the supply pipes, service reservoirs and distribution pipes must be
properly proportioned. The water is supplied by pumping directly and the pumps and
distribution system must be designed to meet the peak demand. The effect of monthly
variation influences the design of storage reservoirs and the hourly variations influences
the design of pumps and service reservoirs. As the population decreases, the fluctuation
rate increases.
Maximum daily demand = 1.8 x average daily demand
Maximum hourly demand of maximum day i.e. Peak demand
= 1.5 x average hourly demand
= 1.5 x Maximum daily demand/24
= 1.5 x (1.8 x average daily demand)/24
= 2.7 x average daily demand/24
= 2.7 x annual average hourly demand

4.1Design Periods & Population Forecast
This quantity should be worked out with due provision for the estimated requirements of
the future. The future period for which a provision is made in the water supply scheme is
known as the design period.
Design period is estimated based on the following:
Useful life of the component , considering obsolescence, wear, tear, etc.
Expandability aspect.
Anticipated rate of growth of population, including industrial, commercial
developments & migration-immigration.
Available resources.
Performance of the system during initial period.
4.2Population Forecasting Methods
The various methods adopted for estimating future populations are given below. The
particular method to be adopted for a particular case or for a particular city depends
largely on the factors discussed in the methods, and the selection is left to the discrection
and intelligence of the designer.
1. Incremental Increase Method
2. Decreasing Rate of Growth Method
3. Simple Graphical Method
4. Comparative Graphical Method
5. Ratio Method
6. Logistic Curve Method
7. Arithmetic Increase Method
8. Geometric Increase Method
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Hi
I want book of design steps of overhead rectangular water tank pdf
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